The cheapest astronomical telescope

Astronomical telescope is the "eye" for human beings to observe and understand the universe, and it is the most used and symbolic astronomical observation equipment; It is used to help users observe the details that are difficult to distinguish with the naked eye in the starry sky and look for distant and dim celestial bodies.

Basic knowledge of astronomical telescope:

A, optical astronomical telescope:

1, refractive type: easy to use, large field of vision, bright star image, but chromatic aberration, which will reduce the resolution, and easy to use and maintain.

2. Reflective type: there is no chromatic aberration, but coma and astigmatism are large, which makes the edge image of the visual field worse; Newton mirror is commonly used, and its optical system is simple. At the same price, the available mirror has the largest aperture and the strongest light collection ability.

3. Refraction: It combines the advantages of refractor and reflector: large field of view, good imaging quality, short lens barrel and easy to carry. There are two types: Schmidt-Ka seglin and Maksutov-Ka seglin.

Second, the basic optical performance parameters of astronomical telescope:

1, aperture: The effective aperture of the objective lens theoretically determines the performance of the telescope. The larger the aperture, the stronger the light gathering ability, the higher the resolution and the larger the available magnification.

2. Concentrating power: Concentrating power, the ratio of the light received by the telescope to the light received by the naked eye. The diameter of a person's pupil is about 7mm when it is fully opened. 70mm diameter telescope, the light collection capacity is 702/72= 100 times.

3. Resolution: The ability of the telescope to distinguish image details. Resolution is mainly related to aperture;

4. Magnification: the ratio of the focal length of the objective lens to the focal length of the eyepiece. For example, Pioneer 60/700 astronomical telescope uses H 10mm eyepiece, and the magnification = objective 700mm/ eyepiece 10mm = 70 times; The larger the magnification, the larger the image you see.

The larger the magnification, the better. Generally, the maximum available magnification is not more than 1.5 times the aperture mm. When the maximum effective magnification is exceeded, the image will become larger, but the definition will not be improved.

5. Focal length ratio: the ratio of the focal length of the objective lens to the aperture, which is equivalent to the aperture on the camera lens. If the aperture is constant, the longer the focal length of the objective lens is, the greater the focal ratio is, and it is easy to obtain higher magnification; The shorter the focal length of the objective lens, the smaller the focal ratio, and it is not easy to get a higher magnification, but the image is brighter and the field of view is larger.

* short focal length mirror (small focal length ratio, focal length ratio

* long focal length lens (large focal ratio, focal ratio >; 15): suitable for observing the moon and planets;

* medium focal length mirror (medium focal length ratio, 6

Both can be used, which is very suitable for beginners.

6. field of view: the angle of the sky area imaged by the telescope in the eyes of the observer, also known as the field of view angle. The larger the magnification, the smaller the field of view.

7. Limit magnitude: It is the darkest magnitude that can be observed by a telescope, which is mainly related to aperture and focal ratio. People with normal vision can see a 6-magnitude star in the darkest place in dark and transparent air, while the light collection capacity of 70mm telescope is 100 times that of the naked eye, and they can see a 6-magnitude star that is 5 times darker than a 6-magnitude star.

Three, astronomical telescope bracket mechanism

1, horizon type: simple structure and use, low adjustment accuracy, unable to track celestial bodies, suitable for beginners;

2. Equatorial instrument: The equatorial instrument is used to offset the rotation of the earth and track the movement of celestial bodies during observation; Complex structure and use, high adjustment accuracy; There are manual and electric magnetic declination meters. Manual declination tracker is suitable for special astronomical observation, and high-grade electric declination tracker is mostly used for special astronomical tracking photography and observation research.

Beginners can choose manual declination instrument after they are familiar with horizontal support; The first adjustment may be complicated, but it will be much easier to observe the starry sky after familiarity; Amateurs often use the equatorial plane of the electric track when learning astrophotography.

Discrimination of optical quality of astronomical telescope;

During the day, you can use a telescope to observe distant buildings and move the outline of the buildings to 1/4 of the field of vision. If the orange or blue-purple on the outline is particularly obvious, or the outline is particularly curved, the optical quality will be poor. Look at the leaves in the distance Generally, a telescope with a diameter of 60mm can see the Ye Jin of leaves 40 meters away, indicating that the optical quality is very poor (60/700 tube wave pioneers can see the leaves of phoenix trees 60 meters away); When observing stars at night, if you see stars with obvious colors, or the stars at the edge of the field of vision are dragging their tails, the length of the tails is twice that of the stars, indicating that the optical quality is very poor and not suitable for astronomical observation;

* Choose 3 1.7mm( 1.25 inch) large eyepiece interface to obtain better optical quality.

Selection of astronomical telescope;

1、

Telescopes are worth every penny, so don't covet cheap and small workshop products. Some well-known telescope brands in China (such as Guanbo, Sirius, Jinghua, etc. ) the quality and reputation are good, and there are regular sales points, which can be selected on the spot.

2、

According to the individual's economic ability, try to choose a large-caliber telescope;

For beginners, it is recommended to choose 60mm, 70mm and 80mm caliber refractors:

* It is convenient to carry, use and maintain, and can be taken out for observation frequently (100mm or more is relatively overweight and difficult to carry; How much depends on the number of observations rather than the diameter of the telescope);

* Even in cities with severe light damage, you can watch sunspots, the moon and bright celestial bodies such as Jupiter and Saturn;

* Low price, buy a bigger and better telescope in the future, and upgrade it to a star guide mirror to make full use of it;

Matters needing attention in the use of astronomical telescope:

1, you must never watch the sun directly through a telescope, and you must watch the sun through projection or special filtering measures;

2, don't use the telescope as a toy, the telescope is a precision optical instrument, so be careful to use and maintain it;

Don't think that you can see everything with a telescope. You can really see celestial bodies and details on celestial bodies through telescopes, but the better the viewing effect, the higher the price. There is no perfect telescope, so it is most important to choose the one that suits you.

4. Every telescope has its proper magnification. Exceeding this multiple will not enhance the resolution, but will make the object very dark and difficult to see. For a telescope with a diameter of 60 ~ 80, the appropriate magnification should be less than 100, and almost nothing can be seen when magnified 200 times.

5. If you can't identify more than five constellations in the night sky, don't use a telescope in a hurry, because you can't find observable stars, you can only look at the moon;

6. Astronomical telescopes can usually watch landscapes or animals and plants, and can easily get a higher magnification than binoculars. However, the usage ratio should be below 100 times, and 20-50 times is the most suitable.